1. Field of the Invention
The present invention relates generally to controls for agricultural implements and, more specifically, to an opener assembly providing separate placement of two materials such as fertilizer and seed, and an opener disk for such an assembly.
2. Related Art
Opener assemblies such as those on the commercially available John Deere model 750 Grain Drill include a flat disk operating at an angle to the forward direction and a gauge wheel supported closely adjacent the disk for adjusting penetration depth and for cleaning the leading side of the disk. Such an opener assembly is shown in U.S. Pat. No. 4,760,806. A seed tube extends along the trailing side of the disk at least partially in the shadow of the disk to deposit seed in a furrow formed by the opener assembly, and a trailing seed firming wheel establishes good contact between the seed and the ground. In some operations, it is desirable to deposit fertilizer at one level and seed at another level to avoid seed contact with the fertilizer and to optimize nutrient availability for young plants. If fertilizer is placed directly with the seeds, germination damage can occur and use of nitrogen is severely limited. Placing fertilizer beside and below the deposited seed in a single operation reduces the number of passes over the field and can conserve soil moisture. However, maintaining the proper seed bed is a problem since the fertilizer opener tends to disturb soil; this soil disturbance also reduces the moisture-saving advantages of the single pass. To reduce excessive soil disturbance, planting speeds must be reduced. Single elements with dual placement function often fail to operate satisfactorily in certain soil types and conditions and often have heavy draft requirements and less than optimum wear characteristics.
Recently, dual placement systems such as the Flexi-Coil Ltd. Barton.TM. Double Shoot opener have become available. The Barton.TM. system includes a first large reverse-angled disk wherein the top of the disk leans toward the trailing side of the disk. The large disk forms a slot for fertilizer. A cleaning wheel runs closely adjacent the large disk. A second oppositely angled disk located a substantial distance behind the large disk forms a new slot in the soil above and to one side of the fertilizer slot for the seed. The Barton.TM. type of system has several disadvantages including lack of accurate depth control for the trailing disk caused by the large distance between the disk centers. The fore-and-aft dimension of the opener system increases side loads during turns and thereby limits the amount the implement can safely be turned from the forward direction while the openers are operating in the soil. The opener also lacks good separation of materials in certain soil types caused by absence of a device to close the fertilizer trench prior to opening the seed trench. For example in heavy, moist clay conditions the soil fails to fall back into the fertilizer trench. Separation again is a function of the operating speed, with slower speeds being necessary in some conditions to assure separation of seed and fertilizer to prevent germination damage.
Another example of a dual placement opener shown in U.S. Pat. No. 2,920,587 includes a leading flat disk opening a fertilizer furrow and an overlapping trailing flat seed furrow opening disk providing separation of the seed from the fertilizer. A depth control wheel is secured to the leading disk. Such an opener is subject to dirt build-up, depth control is less than optimum, and the trailing disk is upright and does not provide good firming of the soil over the fertilizer. The trailing press wheel running in the seed furrow fails to adequately cover the seed with soil. Lack of an adequate closing systems results in soil erosion problems. The opener is only suitable for tilled soil and would not withstand the rigors of no-till since the forward fertilizer boot or shoe is not in the shadow of the trailing disk for protection. The trailing seed shoe is offset a substantial distance from the protective shadow of the leading disk and is offset at an angle of four to five degrees to the plane of forward travel. The seed shoe has a forward curved edge outside the shadow of the trailing disk. The large offset significantly increases draft forces in untilled soil, and portions of the seed and fertilizer boots create a lot of soil disturbance. In no-till conditions, residue and soil builds up, especially at the curved forward edge of the trailing seed shoe. The trailing seed boot in this and other dual placement openers lies outside the shadow of the disk which not only increases draft but also increases potential for disk and seed boot wear and damage. Bearings extending outwardly from the disk shadow are subject to damage and can catch trash, particularly in narrow row, minimum tillage conditions.